Intergrated cement delivery system for bone augmentation procedures and methods

ABSTRACT

A cement delivery system for vertebroplasty including a rigid cannula having a tubular inner wall defining a central conduit to deliver bone cement and a tubular outer wall extending around the inner wall and spaced apart therefrom to define a peripheral conduit for aspirating bone fluids. Aspirating means communicate with a proximal outlet port of the peripheral conduit to create a pressure gradient between the central conduit and the peripheral conduit to provide a hydraulic force guiding the displacement of bone fluid and the flow of cement. Also, a bone cement delivery system including a rigid cannula having a tubular inner wall defining a central conduit, a tubular outer wall extending around the inner wall and spaced apart therefrom to define a peripheral conduit, and a tubular middle wall extending between the inner and peripheral walls and spaced apart therefrom to define a middle conduit around the central conduit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of PCT Patent Application No.CA2007/000579 filed Apr. 5, 2007, which claims priority on U.S.Provisional Patent Application No. 60/789,891 filed Apr. 7, 2006, bothof which are incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for performing boneaugmentation procedures, and more particularly to a cement deliverysystem for such procedures and to a method for the use of such a system.

BACKGROUND ART

A number of different types of bone cement injection procedures areroutinely practiced, among which is vertebroplasty.

Unfortunately, the pressure required to inject cement can easily reachvalues beyond human physical limit. A number of pressure-controlleddevices are available to increasing the pressure applied to the cementfor delivery, however such devices may increase the risk of cementleakage because of a lack of control on the cement flow rate. It is alsoknown to lower the cement viscosity to ease the injection, however suchan approach may also generally increase the risk of cement leakage.

While most cement leaks are inconsequential, every leak neverthelessexposes patients to serious risks, such as spinal cord and nerve rootcompression, pulmonary embolism, and possibly even death.

Further, the viscosity of the bone cement changes as the cementpolymerizes, while also varying substantially due to various factorssuch as environmental conditions (e.g. temperature, humidity), themixing technique used, as well as the batch and type of cement used.Physicians often use suggestive methods such as visual and/or tactileinspection to evaluate whether the viscosity of cement is adequate forinjection, such methods being generally imprecise and not easilyreproducible.

Accordingly, improvements are desirable.

SUMMARY OF INVENTION

In accordance with the present invention, there is provided a bonecement delivery system for vertebroplasty comprising a rigid cannulahaving a tubular inner wall defining and surrounding a central conduitto deliver bone cement into a vertebra under pressure, the inner walldefining a distal outlet port of the central conduit at a distal end ofthe cannula, a tubular outer wall extending around the inner wall andspaced apart therefrom to define a peripheral conduit around the centralconduit for aspirating bone fluids, the outer wall defining a distalinlet port of the peripheral conduit at the distal end of the cannula,the outer wall having an outer diameter not exceeding acceptableparameters for vertebroplasty, a proximal end of the cannula including aproximal inlet port in communication with the central conduit and aproximal outlet port in communication with the peripheral conduit, andaspirating means communicating with the proximal outlet port of theperipheral conduit to create a pressure gradient between the centralconduit and the peripheral conduit to provide a hydraulic force guidingthe displacement of bone fluid and the flow of cement.

Also in accordance with the present invention, there is provided a bonecement delivery system comprising a rigid cannula having a tubular innerwall defining and surrounding a central conduit for bone cementdelivery, the inner wall defining a distal outlet of the central conduitat a distal end of the cannula, a tubular outer wall extending aroundthe inner wall and spaced apart therefrom to define a peripheral conduitaround the central conduit, the outer wall defining a distal inlet ofthe peripheral conduit at the distal end of the cannula, and a proximalend of the cannula including a proximal inlet port in communication withthe central conduit and a proximal outlet port in communication with theperipheral conduit, and further comprising a tubular middle wallextending between the inner and peripheral walls and spaced aparttherefrom to define a middle conduit around the central conduit, theperipheral conduit being defined around the middle conduit.

Also in accordance with the present invention, there is provided amedical cannula comprising at least one tubular wall defining andsurrounding an injection conduit, the wall defining a distal outlet ofthe injection conduit at a distal end of the cannula, and a proximal endof the cannula including a proximal inlet in communication with theinjection conduit, and an elastic and permeable membrane covering thedistal outlet of the injection conduit for delivery of injected fluidtherethrough.

Also in accordance with the present invention, there is provided amethod of injecting bone cement within a vertebra, comprising injectingbone cement within the vertebra through a pedicle, and at least one ofaspirating bone fluid from the vertebra through said pediclesimultaneously with the bone cement injection and creating a pressuregradient between the injection and aspiration steps to provide ahydraulic force guiding the displacement of bone fluid and the flow ofbone cement.

Also in accordance with the present invention, there is provided a bonecement delivery device, comprising a syringe body for containing thebone cement, a plunger snuggly and slidably received within the syringebody for pushing the bone cement out of the syringe body, a drivingsystem connected to the plunger and sliding the plunger within thesyringe body, and a control system controlling the driving system in adisplacement-controlled and continuous manner over a given time periodto produce a constant flow of bone cement out of the syringe body withinthe time period based on commands from a user.

Also in accordance with the present invention, there is provided a bonecement delivery device comprising a body for containing the bone cementtherein and for progressively injecting the bone cement therefrom fordelivery into the bone, at least one sensor for measuring a physicalparameter of the bone cement within the body, wherein the sensor isintegral with the body, the at least one parameter being indicative ofcuring of the bone cement, and a display unit receiving data from thesensor and displaying at least one of the physical parameter and thecuring progress of the bone cement.

Also in accordance with the present invention, there is provided amethod of injecting bone cement within a bone, comprising monitoring atleast one parameter indicative of a curing of the bone cement directlywithin a bone cement delivery device, and injecting the bone cement inthe bone with the delivery device based on the at least one parameter.

Also in accordance with the present invention, there is provided acontrol system for a bone cement delivery device, the control systemcomprising a delivery pressure sensor for measuring a cement deliverypressure and producing corresponding delivery pressure data, a controlpanel for receiving commands from a user and producing correspondingcommand data, a driving system for actuating the cement delivery deviceto deliver the bone cement, a control module for receiving the commanddata and the delivery pressure data, and for sending a control signalactuating the driving system based on the command data and the deliverypressure data such as to deliver the bone cement in a steady flow, and adisplay unit for receiving the pressure data from the control module anddisplaying delivery pressure information based on the delivery pressuredata.

Also in accordance with the present invention, there is provided anintegrated cement delivery system comprising a cement delivery deviceincluding a syringe body for containing the bone cement, a plungerslidably received within the syringe body for pushing the bone cementout of the syringe body, and a driving system connected to the plungerand sliding the plunger within the syringe body, an injection pressuresensor measuring an injection pressure of the cement within the syringebody, a control system controlling the driving system in adisplacement-controlled and continuous manner to produce a steady flowof bone cement out of the syringe body based on data from the injectionpressure sensor and commands from a user, and a display unit displayingthe data from the injection pressure sensor.

Also in accordance with the present invention, there is provided amethod of extracting marrow from a vertebra, comprising injecting athick liquid in the vertebra through a single pedicle, displacing themarrow with the thick liquid, and extracting the marrow through saidsingle pedicle simultaneously with the thick liquid injection bycreating a pressure gradient between the injecting and extracting.

Also in accordance with the present invention, there is provided amethod of rinsing marrow within a vertebra, comprising inserting acannula in the vertebra, injecting a liquid in the vertebra through afirst conduit of the cannula, aspirating the marrow and bone fluidthrough a second conduit of the cannula and creating a pressure gradientbetween the first conduit and the second conduit.

Also in accordance with the present invention, there is provided, incombination, a cannula and a syringe body, the cannula defining aninjection conduit having a constant diameter throughout a lengththereof, and the syringe body includes a tapered distal end defining anoutlet connected to the injection conduit of the cannula, the tapereddistal end providing a progressive and constant diameter reductionbetween a remainder of the syringe body and the injection conduit.

Also in accordance with the present invention, there is provided aviscosity sensing unit for a bone cement delivery device, the unitcomprising at least one sensor for measuring a physical parameter of thebone cement directly within the bone cement delivery device, the atleast one parameter being indicative of a viscosity of the bone cement,and a display unit receiving data from the sensor and displaying atleast one of the physical parameter and the viscosity of the bonecement.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the accompanying drawings, showing by wayof illustration particular embodiments of the present invention and inwhich:

FIG. 1 is schematic representation of a cement delivery system accordingto a particular embodiment of the present invention;

FIG. 2 is a tridimensional cross-sectional view of a cannula accordingto a particular embodiment of the present invention;

FIG. 3 is a tridimensional cross-sectional view of a cannula accordingto an alternate embodiment of the present invention;

FIG. 4 is a side cross-sectional view of a screw delivery mechanism ofthe cannula of FIG. 3 according to a particular embodiment of thepresent invention;

FIG. 5A is a side cross-sectional view of a cannula according to analternate embodiment of the present invention;

FIG. 5B is an enlarged, side cross-sectional view of a portion of thecannula of FIG. 5A;

FIG. 5C is an enlarged, side cross-sectional view of a portion of thecannula of FIG. 5A according to an alternate embodiment of the presentinvention;

FIG. 6 is tridimensional view of a proximal end of a cannula, which maybe for example the cannula of any one of FIGS. 2 to 5C, including amembrane according to a particular embodiment of the present invention;

FIG. 7 is a schematic tridimensional view of a proximal end of acannula, which may be for example the cannula of any one of FIGS. 2 to5C, including an intravertebral pressure sensor according to aparticular embodiment of the present invention;

FIG. 8 is a schematic side view of a cement delivery device according toa particular embodiment of the present invention;

FIG. 9 is a schematic side view of a cement delivery device according toan alternate embodiment of the present invention;

FIG. 10 is a schematic side view of a cement delivery device accordingto an alternate embodiment of the present invention;

FIG. 11 is a schematic side view of a syringe and cannula assemblyaccording to a particular embodiment of the invention;

FIG. 12 is a schematic side view of a syringe including injectionpressure sensors according to a particular embodiment of the presentinvention;

FIGS. 13A-13C are schematic front views of syringes including differentultrasound viscosity sensors according to alternate embodiments of thepresent invention;

FIG. 14 is a tridimensional schematic view of a syringe including adielectric viscosity sensor according to an alternate embodiment of thepresent invention;

FIGS. 15A-15B are front and bottom schematic views of a syringe plungerincluding a dielectric or electro-resistive viscosity sensor accordingto an alternate embodiment of the present invention;

FIG. 16 is a graphical representation of an example of the Root MeanSquare of an ultrasound pulse of the ultrasound sensors of FIGS.13A-13C;

FIG. 17 is a graphical representation of an example of the attenuationof the ultrasound pulse of the ultrasound sensors of FIGS. 13A-13C;

FIG. 18 is a graphical representation of an example of a capacity,resistance, impedance and phase of the dielectric sensors of FIG. 14;

FIG. 19 is a block diagram of a control system according to a particularembodiment of the present invention;

FIG. 20 is a tridimensional view of a cement delivery device accordingto a particular embodiment of the present invention;

FIG. 21 is a tridimensional view of a cement delivery device accordingto an alternate embodiment of the present invention;

FIG. 22 is a tridimensional view of a cement delivery device accordingto an alternate embodiment of the present invention; and

FIG. 23 is a tridimensional view of a cement delivery system accordingto a particular embodiment of the present invention, shown here incombination with the cement delivery device depicted in FIG. 22.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Referring generally to FIG. 1, a cement delivery system according to aparticular embodiment of the present invention is generally andschematically shown at 10. The system 10 generally comprises a cannula12 which may include pressure sensors 14 to measure the intravertebralpressure, an assisted cement delivery device 16 delivering cementthrough the cannula 12 and including miniature viscosity sensors 18 tomonitor a viscosity of the cement, a controller or control module 20,such as for example provided in an electronic circuit board including amicroprocessor, for controlling or operating the cement delivery device16, a digital display unit 22 for displaying sensor data during theprocedure, a control or regulation panel 24 for receiving instructionsfrom a user, and a power supply 26 providing power to the system 10.

The different elements of the cement delivery system 10 are separatelydescribed in more detail in the following.

Cannulae 12

The cannula 12 in FIG. 1 can be a standard cannula or, alternately, oneof the cannulae 12 a,b,c shown in FIGS. 2 to 7. The cannulae 12 a,b,cdescribed below allow for monitoring of the intravertebral pressuresand/or aspiration of the vertebral body to drain the bone fluid (e.g.marrow, blood) that is displaced during the cement injection, such as toreduce cement leakage and reduce the risk of emboli. The cannulae 12a,b,c are preferably made of an appropriate type of metal or other rigidmaterial, similarly to known single conduit cannula typically used inbone cement injection procedures.

In the case of vertebroplasty, the total pressure required for cementinjection Δp_(inj) can be separated into the extravertebral cementdelivery pressure Δp_(extra) required to force the cement through acannula, the intravertebral cement infiltration pressure Δp_(inf)required to force the cement to penetrate the vertebral cavity, and theintravertebral bone marrow pressure Δp_(mar) within the vertebral bodydue to the hydraulic resistance of the vertebra, i.e.Δp_(inj)=Δp_(extra)+Δp_(inf)+Δp_(mar). The extravertebral deliverypressure Δp_(extra) is generally the largest (e.g. up to 500 psi formechanical injectors), while the infiltration pressure Δp_(inf) and thebone marrow pressure Δp_(mar) are generally much lower (e.g. 50 psi and5 psi, respectively).

Monitoring of the internal bone pressure, or, in the case ofvertebroplasty, of the intravertebral pressure (i.e. the infiltrationpressure Δp_(inf) and the bone marrow pressure Δp_(mar)) ensures thatthere is no excess pressure in the bone (vertebral) cavity whendelivering cement, as an elevated pressure may cause the cement tospread suddenly in uncontrolled fashion or cause lung emboli. Themonitoring of the internal or intravertebral pressure can also be usedas a predictor of leakage, since a sudden pressure drop may indicate theexistence of a path of least resistance leading to cement leakage. Themonitoring of the internal or intervertebral pressure thus allow forprevention of these complications.

Knowledge of the internal or intravertebral pressures also allows forthe determination of the pressure within the cannula (e.g.extravertebral), which creates a diagnostic tool for the case in whichthe physician is not in a position to deliver cement, for exampleindicating that the cannula is plugged or that the cement is not goinginto the bone (vertebral body).

Referring to FIG. 2, the cannula 12 a includes an outer tubular wall 28a defining a proximal end 30 and a distal end 32. Concentric peripheraland central conduits 34 a, 36 a are separated by a thin tubular internalwall 38 a extending in the cannula 12 a spaced apart from the outertubular wall 28 a. The cannula 12 a includes a side outlet 40 a definedat the proximal end 30 and a series of fenestrations 42 a defined at thedistal end 32, both of which being in communication with the peripheralconduit 34 a. The central conduit 36 a is used to deliver the cement,while the peripheral conduit 34 a is used to aspirate the vertebra toaspirate bone fluid (e.g. marrow, blood) during cement injection, or tomeasure the intravertebral cement infiltration or bone marrow pressuresΔp_(inf) or Δp_(mar) through a pressure sensor 14 (see FIG. 1).

In the case where the peripheral conduit 34 a is used to aspirate thevertebra, the fenestrations 42 a represent a vent or a sink for thedisplaced bone fluid when the cement enters the vertebral cavities. In aparticular embodiment, the aspiration is done manually using a standardsyringe attached to the side outlet 40 a to create a vacuum while thephysician delivers the cement and to remove the bone fluid. In a morepreferred embodiment, the aspiration is done in an automated manner andmore specifically, in a volume controlled manner. The automatedaspiration allows for cement to be injected at a given flow rate and forbone fluid to be aspirated at a slightly higher flow rate, such that thecement follows the displaced bone fluid and takes its place. Onepractical way of producing the vacuum for the automated aspiration is touse a vacuum pump connected to the side outlet 40 a and applying forexample a low-level vacuum in the range of 10 to 100 KPa. The vacuumpump is preferably regulated by a vacuum regulator (e.g. mechanical orelectronic), which is regulated by the control module 20 as will bedescribed in a following section.

In addition to removing bone fluid, the aspiration or vacuum creates apressure gradient between the central conduit 36 a and the peripheralconduit 34 a, which creates a hydraulic force guiding the displacementof the bone fluid and the flow of the cement. This pressure gradient canbe used to guide the cement flow to facilitate controlled andpredictable filling with enhanced mechanical efficacy and reduced cementemboli.

In a particular embodiment where the peripheral conduit 34 a is used tomeasure the intravertebral cement infiltration or bone marrow pressuresΔp_(inf) or Δp_(mar), the pressure sensor 14 (see FIG. 1) is provided atthe proximal end of the peripheral conduit 34 a, and either air orliquid is used as a media to transfer the pressure wave generated in thevertebra when delivering cement from the distal end 32 of the cannula tothe pressure sensor 14.

The cannula 12 a may feature different fenestration patterns at itsdistal end 32 that that shown in order to meet different functions.

The cannula 12 b shown in FIG. 3 is similar to the cannula 12 a, andincludes an outer tubular wall 28 b, concentric peripheral and centralconduits 34 b, 36 b separated by a thin tubular internal wall 38 bspaced apart from the outer tubular wall 28 b, as well as a side outlet40 b at the proximal end 30 and a series of fenestrations 42 b at thedistal end 32 which are both in communication with the peripheralconduit 34 b. Like the cannula 12 a, the central conduit 36 b of thecannula 12 b is used to deliver the cement while the peripheral conduit34 b is used to aspirate and drain the bone fluid as described above, orto measure the intravertebral cement infiltration or bone marrowpressures Δp_(inf) or Δp_(mar) through a pressure sensor 14 (see FIG.1).

However, the cannula 12 b also includes a side inlet 41 defined at theproximal end 30 in communication with the central conduit 36 b, throughwhich the cement enters the cannula 12 b. The cannula 12 b additionallyincludes a screw delivery mechanism 43 extending within the centralconduit 36 b along its length. In a particular embodiment, the screwdelivery mechanism 43 is either a helical or spiral transport screw. Therotating screw delivery mechanism 43 facilitates the transport of thecement through the central conduit 36 b in a precise manner.

The cannula 12 b is thus especially useful for injecting cements thatare difficult to inject because of phase separation, such as for examplecalcium phosphate (CaP), with the screw delivery mechanism 43 increasingthe mixing of the cement to reduce the risk of phase separation. Thescrew delivery mechanism 43 also significant decreases the pressurerequired for cement delivery since the cement delivery by the screwdelivery mechanism 43 requires little pressure when compared with simplypushing the cement though the elongated geometry of the cannula, and assuch can also be used to transport thick PMMA cement. The use of thickcement reduces the risk of leakage, while the use of the screw deliverymechanism 43 facilitates the cement delivery without the need forexcessive forces.

Although the rotation of the screw delivery mechanism 43 can be appliedmanually, in a particular embodiment the rotation is applied by a micromotor (not shown). As such, the pressure drop in the cannula 12 b isovercome by the power of the micro-motor and the physician does notcontribute to overcoming this pressure. The rotation speed of the screwdelivery mechanism 43 is regulated, for example by the control module 20as will be further described below, to adjust for the desired deliveryflow rate. As such, the physician can shift focus on the patient and onthe surgery instead on being focused on delivering sufficient cement inthe intervention. In a particular embodiment, where the central conduit36 b and screw 43 are designed for cement delivery at a speed 3ml/minute, the micro-motor rotating the screw delivery mechanism 43provides a power of approximately 52 mW.

In a particular embodiment, the screw delivery mechanism 43 is a typicaldelivery screw. However, in an alternate embodiment shown in FIG. 4, thescrew delivery mechanism 43 is cannulated, i.e. an inner conduit 37 isdefined within the screw delivery mechanism 43 along its length. Thisinner conduit 37 is preferably instrumented to measure theintravertebral cement infiltration pressure Δp_(inf), with either air orliquid being used for the transfer of the infiltration pressure from thedistal end of the screw to the proximal end of the screw, where apressure sensor 14 (see FIG. 1) is mounted. The screw 43 mayadditionally feature radial fenestrations or vents that connect directlyto its inner conduit 37. The peripheral conduit 34 b is used to measurethe intravertebral bone marrow pressure Δp_(mar) or to aspirate the bonefluid as the bone cement is delivered through the central conduit 36 b.

The cannula 12 c shown in FIGS. 5A-5C includes concentric tubular inner,middle and outer walls 38 c, 39, 28 c, thus defining central, middle andperipheral concentric conduits 36 c, 35, 34 c. A side outlet 40 c (seeFIG. 5A) defined at the proximal end 30 and a series of fenestrations 42c (see FIGS. 5B-5C) at the distal end 32 are both in communication withthe peripheral conduit 34 c. A second side outlet 45 defined at theproximal end is in communication with the middle conduit 35. The centralconduit 36 c is used to deliver bone cement.

Referring particularly to FIG. 5B, in one embodiment, fenestrations 47are defined through the inner wall 38 c, and the middle conduit 35 isused to measure the intravertebral cement infiltration pressure Δp_(inf)while the peripheral conduit 34 c is used to aspirate the bone fluid orto measure the intravertebral bone marrow pressure Δp_(mar). Asdescribed above, in a particular embodiment a pressure sensor 14 (seeFIG. 1) is mounted to the proximal end of the middle conduit 35 andeither air or liquid is used as a media to transfer the pressure wavegenerated in the vertebra when delivering cement from the distal end 32of the cannula to the pressure sensor 14.

In another embodiment shown in FIG. 5C, the fenestrations 47′ arealternately defined through the middle wall 39, and one of the middleand peripheral conduits 35, 34 c is used to measure the intravertebralbone marrow pressure Δp_(mar) while the other is used to aspirate thebone fluid.

Alternately, the screw delivery mechanism 43 of the cannula 12 b, withor without its inner conduit 37, can be integrated in a single conduitcannula or in a cannula having three conduits such as 12 c.

The cannulae 12 a,b,c thus allow for the bone fluid to be aspirated andthe cement to be injected simultaneously and using a same operativesite, without the need to use separate cannulae, which reduces the risksof complications.

The cannulae 12 a,b,c can also advantageously be used to rinse the bonemarrow and create a path favoring cement flow. Prior methods of rinsingthe bone marrow usually necessitate the use of two separate surgicalsites. With the cannulae 12 a,b,c, pulsating or non pulsating fluid isinjected through one of the conduits, creating a pressure gradientbetween the conduits and allowing for the rinsing process to beperformed using a single cannula and thus a single surgical site. Therinsing process is done manually or automatically with the help of anautomated system, applying a level of pressure similar to the oneapplied for bone fluid extraction. In an alternate embodiment, therinsing process is performed through a smaller diameter tubing extendingwithin the cannula (either 12 a,b,c or single conduit cannula) extendingdeeper within the vertebra.

FIG. 6 shows a membrane 44 which is optionally attached at the distalend 32 of the central conduit 36 a,b,c of any one of the cannulae 12a,b,c described above or, alternately, at the distal end of a singleconduit cannula. The membrane 44 is preferably elastic and retractable,and has a permeability (illustrated by holes 46) that is roughly tenpercent (10%) of the permeability of osteoporotic cancellous bone. Thesize and elasticity of the membrane 44 is preferably such as to definean expanded diameter of no more than 5 millimeters to ensure the leastdamage to the surrounding bone. The membrane 44 can be made of fabrictissue or preferably super elastic metals.

When the cement is delivered, it expands the membrane 44 and generates astate of uniform hydrostatic pressure inside the membrane 44.Specifically, the rate of cement flow exterior to the membrane 44 iscontrolled by the pressure gradient between the membrane 44 and thesurrounding bone. The intravertebral pressure in the surrounding bone isinsignificant, thereby imposing a constant uniform pressure gradient onthe surface of the membrane 44. This uniform gradient leads to uniformand controlled flow of the cement through the membrane 44 and in theenvironment. The membrane 44, due to the low permeability, is thus theguiding tool for the intravertebral flow. Thus, the membrane 44 ensurescontrolled slow and uniform expansion of the cement, and preventspreferential pressure gradients caused by local bone morphology andthereby, ensuring seepage flow and likely reducing leakage risk.

In the case where the internal bone pressure (e.g. intervertebralpressure) is not measured through a separate conduit of the cannula, thecannula preferably includes a pressure sensor 14 as shown in FIG. 7,such as a miniature MEM sensor, which is placed directly at its distalend 32 while ensuring that the flow is not obstructed. This providesdirect readings of the internal or intravertebral pressure during thecement delivery process.

As mentioned above, any one of the cannulae 12 a,b,c can take the placeof the cannula 12 in the cement delivery system shown in FIG. 1. Thecannulae 12 a,b,c present the advantage of allowing for multipleoperations (cement delivery and pressure measurements and/or bone marrowextraction and/or bone marrow rinsing) using a single site.

Although the cannulae 12 a,b,c have been described mostly with relationto vertebroplasty, the cannulae 12 a,b,c can alternately be used inother cement augmentation procedures where cement is injected into otheranatomical locations (such as osteoporotic femur and distal radius) andwhere similar issues of high pressure exist. Additionally, the cannulae12 a,b,c can also be used in any appropriate type of percutaneousinjection of viscous biomaterials into the human body (e.g., drugdelivery using carriers, biometrices for tissue engineering).

In addition, the cannulae 12 a,b,c can advantageously be used for bonemarrow extraction for graft, blood disorders, stem cell transplantationor orthopedic procedures. Known methods of performing bone marrowextraction include directly using a syringe to remove the bone marrow,generally extracting mostly blood and a small quantity of marrow. Withthe cannulae 12 a,b,c, a thick liquid is delivered through one of theconduits, invading the bone cavity saturated by bone marrow and as suchdisplacing the bone marrow, which is then guided through suction intoanother conduit of the cannula, thus increasing the efficiency of thebone marrow extraction procedure.

Cement Delivery Device 16

It has been shown that when a fairly liquid cement is injected into avertebra, the cement finds and flows through a path of least resistance,however when the cement is injected at a viscosity or degree of curingthat is high enough, it expands uniformly as if the path of leakage didnot exist. Accordingly, by controlling the time of injection and therebythe cement viscosity, the incidence of leakage can be reducedconsiderably. The challenge is that cement generally ceases to bemanually injectable with a standard syringe and cannula at about theminimal viscosity avoiding flowing through the path of least resistance.

Referring back to FIG. 1, the cement delivery device 16 generallyincludes a syringe body 58 and a syringe plunger 60 which is displacedwithin the body 58 by any adequate driving system 62, such as forexample an electric motor, a pneumatic system or an hydraulic system.The driving system 62 is controlled or regulated by the control module20, as will be described in a following section, such that thedisplacement of the plunger 60 is controlled, preferably advancing in acontinuous manner (i.e. in a consecutive series of steps of equalduration and equally spaced apart, or with an uninterrupted motion at aconstant speed) in the syringe body 58, such as to precisely deliver agiven volume of cement, thus reducing undesired excess cement whichincreases leakage risks. In a particular embodiment, the driving system62 allows for the delivery of a desired volume of cement with aprecision of 50 micro liters. The driving system 62 generates an axialforce on the plunger 60 which generates an injection pressuresubstantially greater than human physical limits and sufficient todeliver the cement, thus overcoming the limitation of excessive pressureand increasing the chances of being able to complete the procedureadequately. In a particular embodiment, the axial force generated by thedriving system 62 is approximately 2 KN. The increased injectionpressure ensures the delivery of thicker cement, which substantiallyreduces the risks of cement leakage.

The driving system 62 delivers the cement continuously and slowly, forexample at 3 ml/minute, and in a particular embodiment, at most 10ml/minute, resulting in a steady flow which enhances cement fillinguniformity and reduces leakage risks by reducing undesired transientpeaks in pressure.

The driving system 62 allows for a displacement controlled deliverywhich leads to stable flow conditions, thereby reducing the risk ofsudden uncontrolled flow in the case of leakage.

Referring to FIG. 8, a particular embodiment 16 a of the cement deliverydevice 16 is shown. The cement delivery device 16 a includes a worm gearspeed reduction mechanism 64 connected to the driving system 62,depicted here as an electric motor. The motor 62 powers the endlessscrew component 66 of the worm gear mechanism 64, which turns the wheelcomponent 68 that rotates a threaded rod 70 a. The threaded rod 70 a isrotationally supported between two supports 72, which also support aguidance rod 74 extending therebetween. A nut 76 is slidably retained bythe guidance rod 74 and threadingly engaged to the threaded rod 70 a.The rotation of the threaded rod 70 a causes a lateral motion of the nut76 and of a pushrod 78 a connected thereto, the pushrod 78 a activatingthe movement of the syringe plunger 60 within the body 58 of the syringe114 to inject the cement. The guidance rod 74 ensures steady movement ofthe pushrod 78 a for accurate cement delivery.

A number of alternate embodiments are possible. For example, in onealternate embodiment, the nut 76 is omitted, and the rotation of thethreaded rod 70 a directly applies a lateral force to the pushrod 78 awhich is threadingly engaged therewith and slidably received on theguidance rod 74. In another alternate embodiment, the pushrod 78 a isomitted, and the nut 76 directly activates the movement of the plunger60. In another alternate embodiment, the guidance rod 74 and pushrod 78a extend on opposed sides of the syringe body 58 for improved stability.In another alternate embodiment, the supports 72 can directly supportand guide the threaded rod 70 a, pushrod 78 a and/or nut 76, and as suchthe guidance rod 74 can be omitted. In another alternate embodiment, thepushrod 78 a or the nut 76 acts directly as the syringe plunger 60, thusreducing the number of necessary elements. Other modifications are alsopossible.

Referring to FIG. 9, another particular embodiment 16 b of the cementdelivery device 16 is shown. The cement delivery device 16 b includes aspur gear and toothed rack speed reduction mechanism 82 connected to thedriving system 62, shown here as an electric motor, through a pinion 80.The motor 62 rotates the pinion 80, which rotates the spur gear 84 ofthe mechanism 82, which in turn forces the movement of the toothed rack86. The rack 86 is fixed to the pushrod 78 b, so the movement of therack 86 applies a lateral force to the pushrod 78 b which activates themovement of the syringe plunger 60 inside the body 58 of the syringe 114and forces the injection of the cement.

Referring to FIG. 10, another particular embodiment 16 c of the cementdelivery device 16 is shown. The cement delivery device 16 c is simpleand the driving system 62, whether electrical, pneumatic, hydraulic orother, is a linear motor, directly rotating and translating a threadedrod 70 c. The threaded rod 70 c is attached to an interchangeable head88 that acts as the plunger 60 within the body 58 of the syringe 114.The lateral movement of the head 88 forces the injection of the cement.

Accordingly, any one of the devices 16 a,b,c can take the place of thecement delivery device 16 in the cement delivery system 10 shown in FIG.1.

Any one of the devices 16 a,b,c can also be used in any appropriateorthopedic application where medical cement is injected.

Referring to FIG. 11, as suddenly contracting geometry from the cementdelivery device 16 to the cannula 12 in conventional procedures cancauses a substantial increase in injection pressure, in a particularembodiment the geometrical transition from the device 16 to the cannula12, 12 a,b,c is adapted, thereby minimizing unnecessary pressure loss.The diameter of the central conduit 36 a,b,c of the cannula is constant,even in its proximal end 30, where the outer tubular wall 28 a,b,cdefines a connection element 87 such as for example a male Luer lockadapter. The syringe body 58 is tapered, for example defining a conicalshape extending at an angle α (which in a particular embodiment isapproximately 45°) from a remainder of the syringe body 58, up to acomplementary connection element 89, such as for example a complementaryfemale Luer lock adapter, surrounding the connection element 87 of thecannula 12, 12 a,b,c. This provides a smooth transition between thediameter of the major part of the syringe body 58 and the constantdiameter of the central conduit 36 a,b,c, thus lowering the overallinjection pressure, and as such facilitating the delivery of thickercements. Such a connection can alternately be used in other types ofsyringes and delivery systems for cements or other thick medium,including manual delivery systems.

Referring to FIG. 12, in a particular embodiment the cement deliverydevice 16 (16 a,b,c, or other) is instrumented to measure the injectionpressure. The device 16 comprises injection pressure sensors 90including a strain gauge bridge 92 embedded directly in the syringeplunger 60, such as to measure the overall injection pressure during thecement delivery process. In an alternate embodiment, the injectionpressure sensors 90 include a force or loading cell embedded between theplunger and the displacing mechanism of the plunger. An example for sucha load cell is a cylindrical load cell with two threads protruding fromboth sides.

The injection pressure can be calculated once the injection force andthe cross-sectional area of the syringe are known. The injectionpressure sensors 90, whether in the form of force sensors or in anyother adequate form, can alternately be included in any otherappropriate location of the cement delivery device 16, 16 a,b,c, such asfor example within the driving system 62.

With the knowledge of the injection pressure and of the internal bonepressure (e.g. intravertebral), the pressure drop in the cannula 12 canbe determined, and as such, based on the known injection speed andcannula dimensions, the viscosity of the cement can be determinedthrough Hagen-Poiseuille's law.

Viscosity Sensor 18

As shown in FIG. 1, the cement delivery system 10 further includesviscosity sensors 18 providing continuous viscosity or curing readingsof the polymerizing cement in the cement delivery device 16, withoutintroducing any significant changes to the technique of vertebroplasty.

The role of cement viscosity or the degree of polymerization plays asignificant part in the safety of vertebroplasty. More specifically,cement having a higher viscosity enhances the uniformity of the cementfilling, thereby reducing the risk of cement leakage. Specifically, theviscosity sensors 18 monitor changing physical properties triggered bythe cement polymerization. In particular embodiments, the sensorsmonitor acoustic properties of the cement, while in alternateembodiments the sensors monitor electrical properties of the cement.Alternately, other properties of the cement can be monitored, forexample using piezo-electric sensors, a conductive grid, photonicsensors, reflective sensors, spectroscopic sensors, etc. The viscositysensors 18 can be used in vertebroplasty but also in cement guns ordelivery systems used in arthroplasty, or in any medical interventionwhere bone cements are used and where physicians require cementviscosity readings.

In particular embodiments shown in FIGS. 13A-13C, the miniatureviscosity sensors 18 a,b,c include an ultrasound emitter 94 a,b,c and anultrasound receiver 96 a,b,c positioned around the syringe body 58. Theemitter 94 a,b,c sends out an ultrasound signal that goes through thecement and reaches the receiver 96 a,b,c. The sensors 18 a,b,c measurethe pulse attenuation, time delay, traveling speed, and the intensity ofthe ultrasound signal. These quantities change as the cement polymerizesin the syringe body 58. When these readings are known, the cementproperties are determined accurately. The sensors 18 a,b,c arenon-invasive and non-intrusive, forming an integral and reusable part ofthe cement delivery system 10. The ultrasound signal can be longitudinalor transversal.

In the embodiment shown in FIG. 13A, both the emitter 94 a and receiver96 a of the sensor 18 a are integrated into one unit. In the embodimentshown in FIG. 13B, the emitter 94 b and receiver 96 b of the sensor 18 bare two isolated entities or components that are located at the oppositesides of the syringe body 58. In the embodiment shown in FIG. 13C, thereceiver 96 c and emitter 94 c are positioned at two different locationsone a same side of the syringe body 58.

The initial pulse and the attenuated pulse are triggered, controlled orregulated and analyzed by the control module 20 (see FIG. 1), as will bedescribed in a following section.

The display unit 22 (see FIG. 1) displays various information obtainedfrom the sensors 18 a,b,c, which include for example: the attenuation ordampening of the original signal compared to the received signal, thevelocity at which the signal travels through the cement, the delay timewhich is the time taken by the pulse to travel through the cement, andthe Root mean square (RMS) which measures the intensity of the receivedsignal. The delay time and the velocity are interrelated because of thefixed diameter of the syringe.

In alternate embodiments shown in FIGS. 14-15 the miniature viscositysensors 18 d,e include dielectric or electro-resistive sensors. Thedielectric sensors measure the capacitive and conductive properties ofthe polymerizing cement, and the electro-resistive sensors measure theresistive properties of the cement. An advantage of the dielectric andelectro-resistive sensors is that they can be integrated in theelectronic circuit board including the control module 20.

In the embodiment shown in FIG. 14, the dielectric sensor 18 d isreusable and is an integral component of the cement delivery system 10.This sensor 18 d comprises two thin metallic plates 98 with a convexgeometry, or any other appropriate geometry, adapted to partiallysurround the syringe body 58 and defining a capacitor or condenser. Thetwo plates 98 are spring loaded through springs 100. Once the standardsyringe body 58 is placed between the two plates 98, the springs 100clamp the syringe body 58 and ensure direct physical contact between thetwo plates 98 and the syringe body 58 filled with the cement. Analternating current is sent through the two plates 98 and the reading ofthe capacitive and conductive changes on the digital display provideinformation on the cement polymerization process.

In a particular embodiment, the syringe body 58 has an elliptical orrectangular cross-section, which increases the uniformity of theelectric field and as such the stability of the measurements. Therectangular cross-section, or alternately, a square cross-section (thecorners of which can be rounded to facilitate sealing with the plunger)advantageously increases the capacity and also provide the advantage ofensuring that the distance between the plates 98 is constant and known,which further increases the stability of the measurements. Alternately,the syringe body 58 can have a more standard round cross-section.

In an alternate embodiment, the plates are integrated into the standardsyringe body 58, thereby leading to an instrumented disposable syringe.Electroless metallic coating can be used to coat the syringe body 58 toform the plates. The functional thickness of the plates is preferably nomore than a few microns, mainly because of the capacitive and conductivechanges that take place on the atomic level. In a non-invasive versionof the sensor, the thin plates are placed on the outer surface of thesyringe body 58, in a geometry similar to that of the plates 98 shown inFIG. 14 to define a capacitor or condenser. In an invasive version ofthe sensor, which can be either a dielectric or an electro-resistivesensor, the plates are positioned on the inner surface of the syringebody 58 (not shown) or on the tip of the plunger 60 to form the sensor18 e shown in FIG. 15. In both cases, the plates act as electrodes ofthe electro-resistive sensor or as a capacitor of the dielectric sensor.Such instrumented syringes can be produced on a large scale atreasonable cost.

For both reusable and disposable sensors, the electrical signalsindicating the change in the capacitive and conductive properties orresistive properties of the cement is processed and analyzed by thecontrol module 20, and displayed on the display unit 22 of the system 10(see FIG. 1), as will be further detailed in a following section.

Any one of the viscosity sensors 18 a,b,c,d,e can take the place of theviscosity sensor 18 of the cement delivery system 10 shown in FIG. 1.The viscosity sensors 18 a,b,c,d,e can define, together with the displayunit 22, a viscosity sensing unit which can be used in any medicalintervention where bone cements are used and where physicians requirecement viscosity readings, and in combination with any other appropriatecement delivery device 16.

Ultrasound Miniature Viscosity Sensor Experiment

The ultrasound viscosity sensors 18 a,b,c were tested according to thefollowing. An ultrasound pulse was sent to a 10 cc syringe, and the RootMean Square (RMS), attenuation, and the velocity were measured. We alsoexamined the use of longitudinal versus transverse ultrasound waves inaddition to two frequencies of 1 and 5 MHz, although it should beunderstood that other frequencies can be used. The emitter and receiverwere positioned around the syringe using a custom made holder. A pulsegenerator was used to trigger the initial pulse. The attenuated pulsereceived was amplified and displayed on the oscilloscope. The data wasprocessed and analyzed using a pc.

The results of the experiment are shown in FIGS. 16-17. The timesindicated in these figures represent the time after cement mixing. Time0 is the point in time where the two components were mixed. Likewise,time 600 is ten minutes after cement mixing. FIG. 16 shows theevolutions of Root Mean Square (RMS) over the period of polymerizationof the cement. The curve shows an initial plateau, followed by asignificant drop and a slight increase. The curve also shows interestingfeatures around 600 seconds and 800 seconds after the mixing. FIG. 17shows the attenuation of the signal over time. Both figures showconstant change up to roughly 7 minutes. Within two minutes thereafter,there is a significant increase because of the polymerization. Finally,the signal levels off. These two curves are similar to the viscositycurve or the heat production curve when testing cement in a rheometer ora calorimeter.

Dielectric Miniature Sensor Experiment

The dielectric viscosity sensors 18 d,e were tested according to thefollowing. In the reusable embodiment, a sensor was custom made to hostthe syringe filled with cement. In the disposable embodiment, a metalliccoating was used to produce the plates on the outer surface of thesyringe. Also, some measurements have been taken with an invasivedisposable dielectric sensor. For the data acquisition, a RCL meter wasused to replace the control module 20 of the system 10 and to measurethe capacitive and conductive changes of the cement.

The results are shown in FIG. 18, where the times depicted in thefigures indicate the point in time after the cement has been mixed. FIG.18 shows both the capacitive as well as the conductive changes measuredwhen using the non-contact sensor. It is used as a representation of theresults that can be obtained from a dielectric sensor. The figuredepicts that significant changes in both capacitive and resistivechanges take place as time proceeds and these changes are reproducibleand can be used to monitor the advancement of cement polymerization.

Control System 102

Referring to FIG. 19, in a particular embodiment an integrated cementdelivery system such as shown in FIG. 1 includes a control system 102.In a particular embodiment, the control system 102 allows the cementdelivery system 10 to enhance the uniformity of the cement fillingthrough the controlled injection of a cement of adequate viscosity in aprecise and continuous manner, the regulation of the internal andinjection pressures, the immediate depressurization of the vertebra, andthe monitoring and feedback provided to the physician.

The control system 102 comprises the control module 20, theintravertebral pressure sensors 14, viscosity/curing sensors 18,injection pressure sensors 90, control panel 24 and a home positionswitch 104 all sending signals to the control module 20, and the displayunit 22 and driving system 62 receiving signals from the control module20. The home position switch 104 ensures the accurate positioning of thedriving system 62. The switch 104 can be, for example, an optical sensoror a mechanical switch, or an external sensor attached to the cannula12.

The digital display unit 22 is a tool to monitor the cement injectionprocess. The display unit 22 displays data received from the controlmodule 20 such as cement viscosity, total injection pressure, cannuladelivery pressure, intravertebral pressure, cement delivery rate orspeed, total injected volume, etc. All of these readings are displayedgraphically and/or numerically. The display unit 22 can be integrated inthe cement delivery device 16 as will be further detailed below. Inaddition or in the alternative, the display unit 22 can include anexternal large screen connected to the cement delivery device 16 forbetter display and readability.

In a particular embodiment, the control module 20 is provided by anelectronic circuit board (not shown) including a microprocessor, theelectronic circuit board having four objectives: (a) management of thepower supply of the sensors 14, 18, 90 and the driving system 62; (b)gathering and processing signals and instructions from the sensors 14,18, 90 and the physician; (c) advancing the syringe plunger 60 of thecement delivery device 16; and (d) outputting signals for the displayunit 22. The electronic circuit board uses the external power supply 26(see FIG. 1) for objective (a), which in the embodiments shown is a DCpower supply of 24V/1.5-3 A. The control module 20 performs the otherobjectives.

In particular embodiments, the control module 20 has the additionalobjective of controlling the vacuum applied to the cannula 12 a,b,c forbone fluid extraction through a vacuum regulator such as to synchronizethe bone fluid extraction with the cement injection, and/or controllingthe micro-motor rotating the screw delivery mechanism 43 of the cannula12 b.

In the case where a pneumatic or hydraulic cement delivery device 16 isused, the control module 20 regulates the cement delivery processthrough adequate proportional, differential or integral mechanisms forregulation.

In the embodiment shown, the inputs of the control module 20 includeviscosity or polymerization data from the viscosity sensors 18,injection pressure data (such as injection force) from the injectionpressure sensors 90 and intravertebral pressure data from theintravertebral pressure sensors 14. The signals from the sensors 14, 18,90 can be amplified and digitized if required, for example if thesensors 14, 18, 90 generate relatively weak analog output signals.

The inputs received by the control module 20 further include a homeposition signal from the home position switch 104, as well as variouscontrol signals coming from the control panel 24, generated when thephysician uses the command buttons, switches, knobs, etc. of the controlpanel 24. In a particular embodiment, the control signals are digitalsignals. The physician thus controls the injection process directlyusing the control panel 24. In a particular embodiment, the controlsignals from the control panel 24 include, for example, the desiredcement delivery speed and volume, and commands to turn the system on,open the system to insert a syringe body, ready the plunger and syringebody for cement injection, inject the cement, reset for a differentsyringe body, reverse flow direction during the cement delivery,aspirate the bone marrow at a given speed, etc.

The outputs of the control module 20 include one or more actuationsignals to control the driving system 62. In a particular embodiment,the actuation signals include a first signal starting/stopping thedriving system 62, a second signal directing the driving system 62 toturn or translate in one of two opposed directions (e.g. clockwise orcounterclockwise rotation) so that the physician can use the system toboth fill and empty the syringe body 58, and a third signal providingthe speed of the movement of the plunger (e.g. signal in the form of apulse instructing the driving system 62 to move one step, the controlmodule 20 controlling the speed and number of steps, and as such thedisplacement of the plunger 60, through the number and rate of thepulses). In a particular embodiment, a driver (not shown) is interposedbetween the control module 20 and the driving system 62 in order toimplement the actuation signal(s). The driver can be in the form ofhardware or alternately be programmed in the microprocessor of thecircuit board providing for the control module 20.

The other outputs of the control module 20 include the data to bedisplayed on the display unit 22 as mentioned above (e.g. viscosity,pressures, cement delivery rate or speed, total injected volume), aswell as actuation signals to the micro-motor of the screw deliverymechanism 43 and/or to the vacuum system of the cannula 12 a,b,c, ifrequired.

In use and in a particular embodiment, the physician gives a command toopen the device so that a syringe body can be inserted therein, forexample by pressing a corresponding button on the control panel 24 toproduce a corresponding control signal, preferably at the point of timeof cement mixing. This causes the control module 20 to command thedriving system 62 with the corresponding actuation signal(s) to move thesyringe plunger 60 backwards until the home position switch 104 isactivated, emitting the home position signal. Upon reception of the homeposition signal, the control module 20 stops the driving system 62 withthe appropriate actuation signal(s), and the physician inserts the newsyringe body 58. In this example the syringe body 58 is inserted in thedelivery device already filled with cement, however as mentioned abovethe syringe body can alternately be inserted when empty and the systemcan be used to fill the syringe body with cement prior to injection.

When the syringe body 58 is inserted in the cement delivery device 16,the physician gives a second command to move the plunger 60 to aninitial position for injection, for example by pressing a correspondingbutton on the control panel 24 to produce a corresponding controlsignal. This would typically occur soon (e.g. approximately one minuteor less) after mixing of the cement. Upon reception of the controlsignal corresponding to the second command, the control module 20instructs the driving system 62 to move the plunger 60 forward, forexample step by step, with the corresponding actuation signal(s), untilthe injection pressure sensor 90 provides injection force dataindicating that the plunger 60 is beginning to inject the cement fromthe syringe body 58. The control module 20 reads the data coming fromthe injection pressure sensor 90 and the other sensors 14, 18. Uponreception of the adequate injection force data, the driving system 62 isstopped by the control module 20 with the adequate actuation signal(s),and the control module 20 starts to continually send information todisplay on the display unit 22 and/or a computer.

After the plunger 60 is in position, the physician gives a third commandto inject the cement, for example by pressing a corresponding button onthe control panel 24 to produce a corresponding control signal. Thephysician typically gives this third command when the display unit 22shows that the cement viscosity is appropriate. The control module 20reads the data from the sensors 14, 18, 90, and calculates the neededinjection force and the corresponding parameters (e.g. torque, speed) ofthe driving system 62. The control module 20 then activates the drivingsystem 62, and as such the cement injection, through use of thecorresponding actuation signal(s), in order to move the plunger 60 in adisplacement-controlled, continuous manner. As well, at the same time,the control module 20 sends all the necessary information, including thedata from the sensors 14, 18, 90, to the display unit 22 and/orcomputer. In a particular embodiment, the control module 20 only movesthe driving system 62 as long as the physician gives the correspondinginjection command, for example by holding a button depressed in thecontrol panel 24, and if the command is broken (e.g. button released),the control module 20 stops the driving system 62 with the appropriateactuation signal(s) so that the injection is halted.

In a particular embodiment, the control module 20 provides pressurepulsations on the cement during delivery through actuating the drivingsystem 62 in a pulsed manner. Pulsation enhances cement flow, andreduces the delivery pressure. An adequate mode of pulsation changes asthe cement polymerizes. The pulsation mode will likely depend on thecement, and can be determined using a rheometer.

The cement delivery device 16 can also deliver haptic feedback of theintravertebral pressure to the physician. The control module 20 in thiscase gathers intravertebral signals, magnifies them, and sends afeedback signal to generate a contact force on the physician's handduring cement delivery, for example through a portion of the controlpanel 24. This feedback can be integrated in all designs.

Global Design

The cement delivery device 16 can be presented in a plurality of variousexterior designs to achieve the present invention, any one of which caninclude and enclose any one of the mechanisms shown in FIGS. 8-10, acombination thereof, or any other appropriate mechanism transmittingpower from the driving 62 to the syringe plunger 60.

FIG. 20 illustrates a particular embodiment 16 d of the cement deliverydevice 16, which is in the shape of a cement gun and is simple andportable. The device 16 d comprises three principle parts: a body 110 d,a handle 112, and a syringe 114. The body 110 d includes on a top facethereof the display unit 22, for example in the form of a LCD displayscreen, and command buttons 118 forming part of the control panel 24 toensure easy access and utilization, the command buttons 118 allowing thephysician to generate the control signals described above and shown inFIG. 19. The device 16 d is operated by the handle 112, which is solidlyattached to the body 110 d. The handle 112 includes a command button 120on the front thereof to control the cement injection, forming a secondpart of the control panel 24. In a particular embodiment, the commandbutton 120 allows the physician to give the third or injection commanddescribed above.

Once the syringe 114 is filled with cement, it is positioned in acylindrical cavity defined in a block 122 which is part of the body 110d. The device 16 d also includes a translucent syringe support 124 thatis screwed into the block 122. This stabilized the syringe 114 and easesthe injection.

FIG. 21 illustrates another particular embodiment 16 e of the cementdelivery device 16, which is a portable apparatus comprising twoprinciple parts: a body 110 c and a syringe 114. The body 110 e providesan easy to use and consistent interface, including the display unit 22,for example in the form of a large LCD display, and command buttons 126defining part of the control panel 24 and located directly underneaththe display unit 22 for easy access. In a particular embodiment, thecommand buttons 126 allow the physician to generate some of the controlsignals described above and shown in FIG. 19. The body 110 e alsoincludes two flexible levers 128 placed on opposite sides of the displayunit 22 and forming another part of the control panel 24, to allow thephysician to provide others of the control signals described above, suchas for example the desired injection volume and speed of the cement. Thebody 110 e is curved on both sides to allow for comfortable hand controlof the levers 128.

FIG. 22 illustrates another particular embodiment 16 f of the cementdelivery device 16, which is also simple and easy to use. The device 16f is vertically attached to a fixing bar 130, for example by surroundingfastener tightened by a screw, allowing the position of the device 16 fto be easily adjusted on the bar 130.

The device 16 f comprises three principle parts: a body 110 f, thefixing bar 130, and a syringe 114. The body 110 f includes on a sidethereof a syringe support 140 that secures the syringe 114 once it isfilled with cement. A pushrod such as shown for example at 78 a,b inFIGS. 8-9 protrudes from the body 110 f and engages the plunger 60 ofthe syringe 114, such that the movement to the pushrod 78 a,b activatesthe plunger 60 which moves inside the syringe body 58 to force theinjection of the cement.

The device 16 f includes the display unit 22 on a front face of the body110 f, for example in the form of a large LCD display, thus improvingvisibility and access to the results. The control panel 24 is in theform of command buttons 136 placed underneath the display unit 22 wherethey are easily accessible. In a particular embodiment, the commandbuttons 136 allow the physician to generate the control signalsdescribed above and shown in FIG. 19. The body 110 f further includes,on a side thereof, a button 138 to control a light.

FIG. 23 shows a design for the cement delivery system 10 according to aparticular embodiment which allows reduced x-rays exposure for thephysician. The device 16 f of FIG. 22 is shown supported by a flexiblearm 142 which is attached to an upright post 144 extending from a base146. Also supported on the post in an auxiliary control panel 148allowing remote control of the position of the ann 142 and/or the samecontrols/commands provided by the control panel 24. Further supported onthe post are auxiliary display units 150 providing a larger, easier toread display for the information displayed on the display unit 22 and/orany additional pertinent information, such as fluoroscopic visualizationdata. It is understood that the configuration of FIG. 23 can alternatelybe used with any other appropriate design for the cement delivery device16.

The elements of the cement delivery device 10 thus help improve bonecement injection procedures, such as vertebroplasty. The displacementcontrolled cement delivery device 16 a,b,c advantageously provides for acontinuous, slow and precise cement delivery, with an injection pressureexceeding pressures that can be manually applied, thus allowing forthicker cement to be delivered. The viscosity sensors 18 provide forreal time, in-situ monitoring of the cement curing, within the syringebody 58, thus allowing for the cement to be injected at its optimumviscosity. The cannulae 12 a,b,c allow for bone marrow aspirationsimultaneously with bone cement injection, which guides the bone cementwithin the bone as well as reduces the risks of emboli. The cannulae 12a,b,c with an intervertebral or other inner bone pressure sensor 14,either connected to a cannula conduit or embedded in the cannula itself,allow for monitoring of the intravertebral pressure, to ensure thatthere is no excess pressure within the bone, as well as for providing anindication that cement leakage is about to occur or is starting when asudden drop of pressure is detected. The syringe equipped with apressure sensor 90 allows for the determination of the injectionpressure, which provides information on the pressure drop within thecannula and as such on the viscosity of the bone cement. Any one ofthese elements can be integrated in a typical cement delivery system, oralternately be combined with any one, any group of, or all of theothers.

In a particular embodiment, the cement delivery system 10 is anintegrated cement delivery system and includes thedisplacement-controlled cement delivery device 16 a,b,c, the pressuresensors 14 and/or 90, the viscosity sensors 18, and the control system102 including the control module 20, the display unit 22 and the controlpanel 24. This integrated system advantageously improves the safety andpredictability of cement delivery, by providing warnings when thepressure is out of normal ranges, controlling the delivery of bonecement, and insuring that the cement has an appropriate viscosity ondelivery to minimize the risk of leakage.

The cement delivery system 10 of the present invention allows thephysician to control cement delivery by deciding on the injection rateand mode, total injection volume, and period of cement delivery. Ifrequired, the physician can adjust and overwrite the settings of thesystem 10.

The rod 70 c is detachably connected to the head 88 or piston in thesyringe. As the rod 70 c advances it moves the piston against thecement. If for some reason the physician wishes to reduce the pressureapplied to the cement he/she may press the button to stop the advance ofthe rod 70 c. At the same time the direction of the movement of the rodmay be reversed, for example approximately 0.1 mm in order to reduce thepressure on the cement. Since the rod is attached to the piston, it willbe moved backwards as well. This way the same delivery mechanism can beused for depressurization.

The cement delivery system 10 described herein provides the advantage ofconcomitantly overcoming the limitation of excessive pressure andproviding assistance to enhancing filling uniformity such as to reducethe risk of cement leakage. Additionally, the cost effective system 10can be simply incorporated into the vertebroplasty procedure withoutsubstantially affecting or changing how the procedure is performed.Another advantage is that it provides physicians with real timemonitoring of the cement delivery process, which is vital to guiding theintravertebral flow and preventing leakage, instead of reacting tovisual fluoroscopic clues once leakage has occurred. Thus, the cementdelivery system 10 allows the physician to prevent, or at least reducethe risk of, leakage rather than detecting it.

The system 10 also allows the guiding of the intravertebral cementfilling during cement delivery, for example with the cannulae 12 a,b,c,thereby enhancing filling uniformity and reducing leakage risk. Flowguidance is also improved by delivering cement of adequate viscosity.The miniature viscosity sensors 18 provide constant readings ofpolymerizing cement viscosity such as to inject cement having an optimalviscosity.

The system 10 ensures slow and continuous cement delivery, therebyleading to low intravertebral pressure and enhancing smoothness andprecision of delivery. Accurate cement delivery and low pressure reducesleakage risk. More explicitly, precise delivery ensures exact fillingvolume, thereby reducing undesired excess cement which increases leakagerisk. Continuous delivery results in steady flow, thereby reducingundesired transient peaks in pressure which augment leakage risk.Displacement-controlled delivery leads to stable cement flow conditions,thereby reducing the risk of sudden uncontrolled flow, which isdifficult to monitor under fluoroscopy. Delivery forces of at least 2 KNreduce the risk of insufficient filling when delivering thick cement.With live monitoring of pressures and viscosity during procedures,physicians are alerted by acoustic or visual signals when polymerizingcement attains adequate viscosity of safe delivery. With thisstrengthening tool, physicians are alerted when delivery results in highunsafe pressures. Finally, with slow cement delivery, the physician hassufficient time to monitor intravertebral filling and if necessary tointervene, thereby preventing further leakage. The extended time ofmonitoring and reaction combined with fluoroscopic visualization enhanceprocedural safety.

The system 10, through the designs shown for the devices 16 d,e,f, isergonomically designed. The cement delivery device 16 is light and in aparticular embodiment weighs approximately 0.5 kg. Physicians interactwith it in a simple maimer. The system 10 is also economical in design,with the main components being reusable. Disposable items arespecialized syringes and cannulae, which can be bundled in a set.

The system 10 resulted from a thorough biomechanical understanding ofthe cement delivery process and forces governing the intravertebral flowin vertebroplasty. The system 10 and currently used fluoroscopicvisualization can advantageously complete each other by attacking theproblem from two different, yet, complimentary angles, the system 10allowing a substantial reduction in the risk of leakage while thefluoroscopic visualization allowing the detection of leakage if leakagedoes occur. Thus, when combined together the two methods can provide asafer and more reliable vertebroplasty procedure, assisting thephysician in foreseeing and preventing cement leakage.

In another embodiment, the cannula may be provided with a collar on theexterior wall to serve as a stopper which would limit the penetration ofthe cannula in the pedicle. In a particular embodiment, the collar is asimple annular ring surrounding the exterior wall, spaced apart from theproximal end.

1. A bone cement delivery system for vertebroplasty comprising a rigidcannula having: a tubular inner wall defining and surrounding a centralconduit to deliver bone cement into a vertebra under pressure, the innerwall defining a distal outlet port of the central conduit at a distalend of the cannula; a tubular outer wall extending around the inner walland spaced apart therefrom to define a peripheral conduit around thecentral conduit for aspirating bone fluids, the outer wall defining adistal inlet port of the peripheral conduit at the distal end of thecannula; the outer wall having an outer diameter not exceedingacceptable parameters for vertebroplasty; a proximal end of the cannulaincluding a proximal inlet port in communication with the centralconduit and a proximal outlet port in communication with the peripheralconduit; and aspirating means communicating with the proximal outletport of the peripheral conduit to create a pressure gradient between thecentral conduit and the peripheral conduit to provide a hydraulic forceguiding the displacement of bone fluid and the flow of cement.
 2. A bonecement delivery system comprising a rigid cannula having: a tubularinner wall defining and surrounding a central conduit for bone cementdelivery, the inner wall defining a distal outlet of the central conduitat a distal end of the cannula; a tubular outer wall extending aroundthe inner wall and spaced apart therefrom to define a peripheral conduitaround the central conduit, the outer wall defining a distal inlet ofthe peripheral conduit at the distal end of the cannula; and a proximalend of the cannula including a proximal inlet port in communication withthe central conduit and a proximal outlet port in communication with theperipheral conduit; and further comprising a tubular middle wallextending between the inner and peripheral walls and spaced aparttherefrom to define a middle conduit around the central conduit, theperipheral conduit being defined around the middle conduit.
 3. The bonecement delivery system according to claim 2, further including apressure sensor connected to the proximal end of the cannula such as tosense an internal pressure at the distal end of the cannula through themiddle conduit.
 4. The bone cement delivery system according to claim 1,further including a pressure sensor connected to the proximal outletport such as to sense an internal pressure at the distal inlet throughthe peripheral conduit.
 5. The bone cement delivery system according toclaim 1, further including a rotatable screw delivery mechanismextending within the central conduit along a length thereof.
 6. The bonecement delivery system according to claim 5, wherein the rotatable screwdelivery mechanism includes an inner conduit defined therewithin andalong a length thereof, the inner conduit being concentric with thecentral conduit.
 7. The bone cement delivery system according to claim6, further including a pressure sensor connected to a proximal outlet ofthe inner conduit such as to sense an internal pressure at the distalend of the cannula through the inner conduit.
 8. The bone cementdelivery system according to claim 1, wherein the tubular inner walldefines a rotatable screw delivery mechanism extending within theperipheral conduit along a length thereof, such that the central conduitis defined inside the screw delivery mechanism.
 9. The bone cementdelivery system as defined in claim 1, wherein the pressure gradient iscreated by a vacuum pump communicating with the outlet port of theperipheral conduit.
 10. The bone cement delivery system as defined inclaim 9, wherein the vacuum applied is in the range of 10 to 100 KPa.11. The bone delivery cement system as defined in claim 1, wherein theoutlet port of the central conduit and the inlet port of the peripheralconduit are spaced apart linearly.
 12. The bone cement delivery systemaccording to claim 1, wherein the peripheral wall includes fenestrationsdefined therein in communication with the peripheral conduit.
 13. Thebone cement delivery system as defined in claim 1, further including anelastic and permeable membrane covering the distal outlet of the centralconduit for delivery of injected fluid therethrough.
 14. The bone cementdelivery system according to claim 13, wherein the cannula is used todeliver bone cement, and the membrane has a permeability ofapproximately 10% that of osteoporotic cancellous bone.
 15. The bonecement delivery system according to claim 13, wherein the size andelasticity of the membrane is such as to define an expanded diameter ofat most 5 mm.
 16. A medical cannula comprising: at least one tubularwall defining and surrounding an injection conduit, the wall defining adistal outlet of the injection conduit at a distal end of the cannula,and a proximal end of the cannula including a proximal inlet incommunication with the injection conduit; and an elastic and permeablemembrane covering the distal outlet of the injection conduit fordelivery of injected fluid therethrough.
 17. The medical cannulaaccording to claim 16, wherein the cannula is used to deliver bonecement, and the membrane has a permeability of approximately 10% that ofosteoporotic cancellous bone.
 18. The medical cannula according to claim16, wherein the size and elasticity of the membrane is such as to definean expanded diameter of at most 5 mm.
 19. A method of injecting bonecement within a vertebra, comprising: injecting bone cement within thevertebra through a pedicle; and at least one of aspirating bone fluidfrom the vertebra through said pedicle simultaneously with the bonecement injection and creating a pressure gradient between the injectionand aspiration steps to provide a hydraulic force guiding thedisplacement of bone fluid and the flow of bone cement.
 20. The methodaccording to claim 19, wherein the method comprises aspirating the fluidfrom the vertebra through said pedicle simultaneously with the bonecement injection and measuring an internal pressure of the vertebrathrough said pedicle simultaneously with the bone cement injection. 21.The method according to claim 19, wherein the method comprisesaspirating the fluid from the vertebra through said pediclesimultaneously with the bone cement injection, and wherein injecting thebone cement is performed at a first flow rate and aspirating fluid fromthe vertebra is performed at a second flow rate, the second flow ratebeing higher than the first flow rate such that the injected cementtakes the place of the aspirated fluid.
 22. The method according toclaim 19 further including inserting a cannula in the vertebra throughsaid pedicle, and wherein injecting the bone cement includes injectingthe bone cement through a first conduit of the cannula, and the fluid isaspirated through at least a second conduit of the cannula.
 23. Themethod according to claim 19 wherein the method comprises measuring theinternal pressure of the vertebra, including at least one of measuring acement infiltration pressure required to force the cement to penetrate acavity of the vertebra and measuring an intravertebral bone marrowpressure.
 24. A method of rinsing marrow within a vertebra, comprisinginserting a cannula in the vertebra, injecting a liquid in the vertebrathrough a first conduit of the cannula, aspirating the marrow and bonefluid through a second conduit of the cannula and creating a pressuregradient between the first conduit and the second conduit.
 25. A bonecement delivery device, comprising: a syringe body for containing thebone cement; a plunger snuggly and slidably received within the syringebody for pushing the bone cement out of the syringe body; a drivingsystem connected to the plunger and sliding the plunger within thesyringe body; and a control system controlling the driving system in adisplacement-controlled and continuous manner over a given time periodto produce a constant flow of bone cement out of the syringe body withinthe time period based on commands from a user.
 26. The bone cementdelivery device according to claim 25, wherein the control systemproduces several short and equal delivery time periods to provide asteady flow of bone cement with an interruption between consecutive onesof the time periods.
 27. The bone cement delivery device as defined inclaim 25, wherein the control system controls the driving system toadvance the plunger in one of a stepped motion including a series ofequally spaced apart steps of equal duration and a constant motion at aconstant speed to produce a steady flow of bone cement out of thesyringe body.
 28. A control system for a bone cement delivery device,the control system comprising: a delivery pressure sensor for measuringa cement delivery pressure and producing corresponding delivery pressuredata; a control panel for receiving commands from a user and producingcorresponding command data; a driving system for actuating the cementdelivery device to deliver the bone cement; a control module forreceiving the command data and the delivery pressure data, and forsending a control signal actuating the driving system based on thecommand data and the delivery pressure data such as to deliver the bonecement in a steady flow; and a display unit for receiving the pressuredata from the control module and displaying delivery pressureinformation based on the delivery pressure data.
 29. A bone cementdelivery device comprising: a body for containing the bone cementtherein and for progressively injecting the bone cement therefrom fordelivery into the bone; at least one sensor for measuring a physicalparameter of the bone cement within the body wherein the sensor isintegral with the body; the at least one parameter being indicative ofcuring of the bone cement; and a display unit receiving data from thesensor and displaying at least one of the physical parameter and thecuring progress of the bone cement.